Optimization of alkali activated cementless slag concrete production and determination of its mechanical and permeability properties

In this thesis, mechanical (compressive and split tensile strength, abrasion resistance, pullout capacity and ultrasonic pulse velocity) and transport properties (water permeability depth under pressure, sorptivity, water absorption, gas and chloride ion permeability and thermal conductivity) of alkali activated slag concretes were investigated depend on the independent variables such as sodium concentration, silicate modulus, curing temperature and curing time. An experimental program was conducted by using central composite design method. By keeping constant the alkali solution-slag ratio and slag dosage at 0.52 and 400 kg/m3, respectively, twenty one different concrete mixtures were designed. To find out the relations between the independent and dependent variables, statistically significant regression models were developed. Using the developed regression models, multi objective optimization studies were performed to find out the optimum independent variables values under the defined objective functions and constraints. Verification tests were carried out by using the optimum independent variables to reveal the how theoretically obtained optimum values might be implement in real laboratory conditions. Test results revealed that sodium concentration was the most influential independent variable on the mechanical and transport properties of alkali activated slag concretes. Moreover, it was investigated that optimum values of the sodium concentration, silicate modulus, curing temperature and curing times were %5.92, 1.82, 48.3°C and 8.28 hours, respectively, within the range of current research. Key Words: Alkali activation, Ground granulated blast furnace slag, Response surface method, Multi objective optimization